Tuning of non-uniform switch toughening in ferroelectric composites by an electric field

This paper deals with a mode III interfacial crack subject to anti-plane stress and in-plane electric fields. The analysis concentrates on the tuning of fracture toughness from non-uniform ferroelectric-ferroelastic domain switching by an electric field. The electric loading changes the size of the asymmetric switching zone. Employing the weight function method, we obtain the electrically-dependent switch toughening for stationary and quasi-static growing interfacial cracks, respectively. Multi-domain solutions are derived for non-poled and fully-poled ferroelectric composites. Numerical results are presented on the electric field tuning of the critical applied stress intensity factor. The research provides ways to optimize fracture properties of ferroelectric composites by altering the electric field.

Left-Handedness with Three Zero-Absorption Windows Tuned by the Incoherent Pumping Field and Inter-Dot Tunnelings in a GaAs/AlGaAs Triple Quantum Dots System

Left-handedness with three zero-absorption windows is achieved in a triple-quantum-dot system. With the typ- ical parameters of a GaAs/AlGaAs heterostructure, the simultaneous negative relative electric permittivity and magnetic permeability are obtained by the adjustable incoherent pumping field and two inter-dot tunnelings. Furthermore, three zero-absorption windows in the left-handedness frequency bands are observed. The left- handedness with zero-absorption in the solid state heterostrueture may solve the challenges not only in the left-handed materials achieved by the photonic resonant scheme but also in the application of negative refractive materials with a large amount of absorption.

Spin-polarized oscillations of conductance through an Aharonov-Casher ring with a quantum gate

Spin-polarized oscillations in conductance is studied through a mesoscopic Aharonov-Casher （AC） ring with a quantum gate that is tuned by an external magnetic field. Both the conductance and its spin polarization at zero temperature are calculated as a function of the textured electric field, the magnetic field, and Fermi energy. It is found that for some special Fermi energies, spin-up electrons are driven into perfect transmission or reflection states, unaffected by the electric field when Zeeman energy of the incident electrons aligns with one level of the isolated stub or is larger than Fermi energy. This brings about AC oscillations of spin-down conductance. It shows that periodic oscillations of the conductance appear in the adiabatic region of quantum phase and in the normdiabatic region. Anomalous behavior of the conductance oscillation is dependent on the difference between the tilt angle of spin and the electric field.

Tuning the fields focused by a high NA lens using spirally polarized beams(Invited Paper)

We show the power of spirally polarized doughnut beams as a tool for tuning the field distribution in the focus of a high numerical aperture （NA） lens. Different and relevant states of polarization as well as field distributions can be created by the simple turning of a λ/2 retardation wave plate placed in the excitation path of a micro- scope. The realization of such a versatile excitation source can provide an essential tool for nanotechnology investigations and biomedical experiments.

A tuning method for nonuniform traveling-wave accelerating structures

The tuning method of uniform traveling-wave structures based on non-resonant perturbation field distribution measurement has been widely used in tuning both constant-impedance and constant-gradient structures. In this paper, the method of tuning nonuniform structures is proposed on the basis of the above theory. The internal reflection coefficient of each cell is obtained from analyzing the normalized voltage distribution. A numerical simulation of tuning process according to the coupled cavity chain theory has been done and the result shows each cell is in right phase advance after tuning. The method will be used in the tuning of a disk-loaded traveling-wave structure being developed at the Accelerator Laboratory, Tsinghua University.

Electro-lubrication in Janus transition metal dichalcogenide bilayers

Lubrication induced by a vertical electric field or bias voltage is typically not applicable to twodimensional(2D)van der Waals(vdW)crystals.By performing extensive first-principles calculations,we reveal that the interlayer friction and shear resistance of Janus transition metal dichalcogenide(TMD)MoXY(X/Y=S,Se,or Te,and X≠Y)bilayers under a constant normal force mode can be reduced by applying vertical electric fields.The maximum interlayer sliding energy barriers between AA and AB stacking of bilayers MoSTe,MoSeTe,and MoSSe decrease as the positive electric field increases because of the more significant counteracting effect from the electric field energy and the more significant enhancement in interlayer charge transfer in AA stacking.Meanwhile,the presence of negative electric fields decreases the interlayer friction of bilayer MoSTe,because the electronegativity difference between Te and S atoms reduces the interfacial atom charge differences between AA and AB stacking.These results reveal an electro-lubrication mechanism for the heterogeneous interfaces of 2D Janus TMDs.